Enabling Rich Snippets for Reviews and Ratings

Reviews and ratings are two ways to express an evaluation about a range of items.
A review is the evaluation described as text, and a rating is an evaluation described
on a numeric scale (such as 1 to 5). A rating can be marked marked up in conjunction
with, and as part of, a textual review.

We support reviews and ratings for a wide range of schema.org types, including
businesses, products, and different creative works such as books or movies.
When Google finds valid reviews or ratings markup, we may show
a rich snippet that includes stars and other summary info from reviews or ratings.

Reviews

A review is someone's evaluation of something. In addition to the text of the
review, the markup can include a reviewRating, which expresses a summary of the
review as a numeric value.

The item that is being reviewed. This needs to be a valid schema.org type. * If review is embedded into another schema.org type, using review property, then there is no need to mark up the itemReviewed property.

Aggregate Ratings

An aggregate evaluation of an item by many people should be marked up as a schema.org/AggregateRating .
The default rating scale is from 1 (worst) to 5 (best), but any scale can be used; see below
for an example. Google may display aggregate ratings as rich snippets or, for certain types of items, answers in
search results, as shown below.

The item that is being rated. This needs to be a valid schema.org type. * If aggregate rating is embedded into another schema.org type, using aggregateRating property, then there is no need to mark up the itemReviewed property.

ratingCount (required*)

Number

The total number of ratings for the item on your site. * At least one of ratingCount or reviewCount is required.

reviewCount (requierd*)

Number

Specifies the number of people who provided a review with or without an accompanying rating. At least one of ratingCount or reviewCount is required.

ratingValue (required)

Number

A numerical quality rating for the item.

bestRating (required*)

Number

The highest value allowed in this rating system. * Required if the rating system is not a 5-point scale. If bestRating is omitted, 5 is assumed.

worstRating(required*)

Number

The lowest value allowed in this rating system. * Required if the rating system is not a 5-point scale. If worstRating is omitted, 1 is assumed.

Ratings that don't use a 5-point scale

By default, Google assumes that your site uses a 5-point scale, where 5 is the
best possible rating and 1 is the worst, but you can use any other scale. If you
do, you can mark up the best and worst ratings, and Google will scale that to
the 5-star system used in rich snippets. The 10-point scale used above does just this.
For further examples see below.

Marking up an aggregate rating

For sites with aggregate ratings (the rating is based on the average of a
collection of ratings rather than on a single rating or review), the process is
similar to the single review case.

Marking up an aggregate rating when there is no best score

This final example shows how to mark up aggregate rating information that isn't
on a 5-point scale, when the best/worst possible ratings are not explicitly
written on the page. The goal is to display not only the average rating, but
also the scale that it's based on.

The content attribute in the meta tag allows you to provide information that
isn't explicitly written on the page. Note that in general Google will not
display content that isn't visible to the end user, but when the best and/or
worst ratings aren't present on the page, using meta with bestRating or
worstRating is allowed.

Review-specific usage guidelines and policies

To be eligible for reviews and ratings rich snippets, be aware of the following
extra guidelines:

Make sure the review or ratings markup refers clearly to a specific product
or service as shown in the examples above. Do this by nesting the review or ratings
within the markup of another schema.org type — such as schema.org/Book or
schema.org/LocalBusiness — or by using that schema.org typed element as a
value for the itemReviewed property.

Make sure the reviews and ratings you mark up are readily available to users
from the marked-up page. It should be immediately obvious to users that the
page has review or ratings content.

Review and rating markup should be used to provide review and/or rating information
about a specific item, not about a category or a list of items. For example,
“hotels in Madrid”, “summer dresses”, or “cake recipes” are not specific items.
See also our structured data policies for multiple entities on the same page.

We will not show review rich snippets for adult-related products or services.

If the markup contains a single review, the author's name needs to be a
valid name. For example, "50% off until Saturday" is not a valid name for a
reviewer.